Disallow negative strides in date_bin()

It's not clear what the semantics of negative strides would be, so throw
an error instead.

Per report from Bauyrzhan Sakhariyev

Reviewed-by: Tom Lane, Michael Paquier
Discussion: https://www.postgresql.org/message-id/CAKpL73vZmLuFVuwF26FJ%2BNk11PVHhAnQRoREFcA03x7znRoFvA%40mail.gmail.com
Backpatch to v14

doc/src/sgml/func.sgml

@@ -10008,12 +10008,8 @@ SELECT date_bin('15 minutes', TIMESTAMP '2020-02-11 15:44:17', TIMESTAMP '2001-0
    </para>
 
    <para>
-    Negative intervals are allowed and are treated the same as positive intervals.
-   </para>
-
-   <para>
-    The <parameter>stride</parameter> interval cannot contain units of month
-    or larger.
+    The <parameter>stride</parameter> interval must be greater than zero and
+    cannot contain units of month or larger.
    </para>
   </sect2>
 

src/backend/utils/adt/timestamp.c

@@ -3843,10 +3843,10 @@ timestamp_bin(PG_FUNCTION_ARGS)
 
 	stride_usecs = stride->day * USECS_PER_DAY + stride->time;
 
-	if (stride_usecs == 0)
+	if (stride_usecs <= 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-				 errmsg("stride cannot equal zero")));
+				 errmsg("stride must be greater than zero")));
 
 	tm_diff = timestamp - origin;
 	tm_delta = tm_diff - tm_diff % stride_usecs;
@@ -4026,10 +4026,10 @@ timestamptz_bin(PG_FUNCTION_ARGS)
 
 	stride_usecs = stride->day * USECS_PER_DAY + stride->time;
 
-	if (stride_usecs == 0)
+	if (stride_usecs <= 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
-				 errmsg("stride cannot equal zero")));
+				 errmsg("stride must be greater than zero")));
 
 	tm_diff = timestamp - origin;
 	tm_delta = tm_diff - tm_diff % stride_usecs;

src/test/regress/expected/timestamp.out

@@ -706,7 +706,10 @@ SELECT date_bin('5 years'::interval,  timestamp '2020-02-01 01:01:01', timestamp
 ERROR:  timestamps cannot be binned into intervals containing months or years
 -- disallow zero intervals
 SELECT date_bin('0 days'::interval, timestamp '1970-01-01 01:00:00' , timestamp '1970-01-01 00:00:00');
-ERROR:  stride cannot equal zero
+ERROR:  stride must be greater than zero
+-- disallow negative intervals
+SELECT date_bin('-2 days'::interval, timestamp '1970-01-01 01:00:00' , timestamp '1970-01-01 00:00:00');
+ERROR:  stride must be greater than zero
 -- Test casting within a BETWEEN qualifier
 SELECT d1 - timestamp without time zone '1997-01-02' AS diff
   FROM TIMESTAMP_TBL

src/test/regress/expected/timestamptz.out

@@ -750,7 +750,10 @@ SELECT date_bin('5 years'::interval,  timestamp with time zone '2020-02-01 01:01
 ERROR:  timestamps cannot be binned into intervals containing months or years
 -- disallow zero intervals
 SELECT date_bin('0 days'::interval, timestamp with time zone '1970-01-01 01:00:00+00' , timestamp with time zone '1970-01-01 00:00:00+00');
-ERROR:  stride cannot equal zero
+ERROR:  stride must be greater than zero
+-- disallow negative intervals
+SELECT date_bin('-2 days'::interval, timestamp with time zone '1970-01-01 01:00:00+00' , timestamp with time zone '1970-01-01 00:00:00+00');
+ERROR:  stride must be greater than zero
 -- Test casting within a BETWEEN qualifier
 SELECT d1 - timestamp with time zone '1997-01-02' AS diff
   FROM TIMESTAMPTZ_TBL

src/test/regress/sql/timestamp.sql

@@ -266,6 +266,9 @@ SELECT date_bin('5 years'::interval,  timestamp '2020-02-01 01:01:01', timestamp
 -- disallow zero intervals
 SELECT date_bin('0 days'::interval, timestamp '1970-01-01 01:00:00' , timestamp '1970-01-01 00:00:00');
 
+-- disallow negative intervals
+SELECT date_bin('-2 days'::interval, timestamp '1970-01-01 01:00:00' , timestamp '1970-01-01 00:00:00');
+
 -- Test casting within a BETWEEN qualifier
 SELECT d1 - timestamp without time zone '1997-01-02' AS diff
   FROM TIMESTAMP_TBL

src/test/regress/sql/timestamptz.sql

@@ -241,6 +241,9 @@ SELECT date_bin('5 years'::interval,  timestamp with time zone '2020-02-01 01:01
 -- disallow zero intervals
 SELECT date_bin('0 days'::interval, timestamp with time zone '1970-01-01 01:00:00+00' , timestamp with time zone '1970-01-01 00:00:00+00');
 
+-- disallow negative intervals
+SELECT date_bin('-2 days'::interval, timestamp with time zone '1970-01-01 01:00:00+00' , timestamp with time zone '1970-01-01 00:00:00+00');
+
 -- Test casting within a BETWEEN qualifier
 SELECT d1 - timestamp with time zone '1997-01-02' AS diff
   FROM TIMESTAMPTZ_TBL